Description of Calymperaceae: Distribution and Distinctive Features.
Calymperaceae include many taxa of primarily tropical and subtropical distribution at low to moderate elevations, with a few reaching temperate latitudes (Edwards, 1980a; Reese, 1993c). The family is widespread throughout tropical forests, and most members are epiphytic. The best distinguishing features of the family appear to be: 1) acrocarpous and mostly corticolous habit, 2) cancellinae (groups of enlarged, hyaline cells with internal and external pores in the leaf bases), 3) lack of a central strand in the stem, 4) bordered and toothed leaf margins, 5) often reduced single peristome (or lacking), and 6) common production of uniseriate gemmae on leaf tips.

History and Taxonomy of the Calymperaceae. The name Calymperaceae first appeared in C. Mueller's Synopsis (1849) as a subtribe, which included Encalypta (no longer considered part of Calymperaceae) and two other genera: Calymperes (11 species) and Syrrhopodon (32 species, with 3 other questionable species). Later, Calymperaceae appeared in a treatment by Jeager and Sauerbeck (1873), this time ranked at the level of tribe, but still including Encalypta Hedwg., Calymperes Sw., and Syrrhopodon Schwaegr. Somewhat earlier, Mitten (1868) pulled the genus Thyridium Mitt. out of the then large and taxonomically confused Syrrhopodon (Mitten, 1868), and one year later (Mitten, 1869), he established the tribe Syrrhopodonteae including only Calymperes and Syrrhopodon.

It was not until 1897 that Calymperaceae was used as a family name by Kindberg, and although much of his taxonomy was rejected, this particular designation stuck. His circumscription included only Calymperes, while Syrrhopodon was classified in the Weisiaceae (=Pottiaceae). Additional analyses by Mueller (1899) provoked the recognition of Hypodontium C. Müll. as distinct from its parent genus Syrrhopodon, and those two genera were placed back into the family Calymperaceae with Calymperes, and Codonoblepharum (Mueller 1901). Brotherus (1901), however, quickly amended this family delineation by recognizing only Syrrhopodon and Calymperes as part of Calymperaceae.

Fleischer (1904, 1923) did much of the pioneering work on the family in the early part of the present century, yet his taxonomic approaches were somewhat radical. He divided the Calymperaceae into two families, Calymperaceae with one genus, Calymperes (following Kindberg, 1897), and a new family, Syrrhopodontaceae including the genera Thyridium, Leucophanella (Besch.) Fleisch., Syrrhopodon, Calymperidium Dozy and Molk., and Calymperopsis (C. Mull.) Fleisch. In a previous revision (1913), Fleischer recognized Calymperopsis as distinct from its parent genus Syrrhopodon.

Brotherus (1924) reunited Syrrhopodon and the other genera placed previously in the Syrropodontaceae with the Calymperes in the more traditionally circumscribed Calymperaceae (following more along the lines of what Mueller had published). His treatment of Calymperaceae did not include the genera Calymperidium or Leucophanella, and with such omissions, Brotherus brought the family down to five recognized genera: Syrrhopodon, Calymperopsis, Hypodontium, Thyridium, and Calymperes. Some contemporary bryo-taxonomists recognize these five genera as the true members of the Calymperaceae and, at the very least, most no longer consider separating Calymperes from Syrrhopodon (Reese et al., 1986b; see next section for further discussion).

Many authors consider Leucobryaceae and Calymperaceae closely allied and have suggested union of the two families (e.g., Andrews, 1947). Andrews (1947) recommended that Leucophanes Brid., Octoblepharum Hew., Arthrocormus Dozy and Molk., and Exodictyon Card. be considered part of the Calymperaceae. Robinson (1971) adopted at least parts of Andrew's view, and later, Crosby and Magill (1981), Magill (1981), and Reese (1984f) followed, with various modifications; e.g., Magill (1981) and Reese (1984f) included only Octoblepharum in the Calymperaceae. Ellis (1985) suggested that Syrrhopodon and Exodictyon are closely related, while Vitt (1982) suggested that Leuchophanes and Octoblepharum and several others be placed in the Calymperaceae, reserving Leucobryaceae for Leucobryum and other genera. Robinson (1985) also suggested retainment of Leucobryacae, but transferred Exodictyon and Leucophanes to Calymperaceae.

Attempts to unite Calymperaceae with Leucobryaceae, or attempts to include "leucobryaceous" genera within the Calymperaceae have so far been rejected by Reese (e.g., 1993c), yet remain a subject in need of an overall phylogenetic evaluation of the family. Reese and various co-workers have paved the way towards clearer understandings of the Calymperaceae and its associated genera (Lin, 1979, 1984, 1989; Lin and Reese, 1989; Mohamed and Reese, 1985; 1988; 1992; Reese, 1957; 1959; 1961; 1974; 1975; 1977; 1978; 1979 a-b; 1981; 1982; 1983a; 1983b; 1984a-f; 1985a,b; 1987a-c; 1989; 1990; 1991a-b; 1992; 1993a-d; 1994a-f; 1995; 1996; Reese and Bartlett, 1982; Reese and Buck, 1991a,b; Reese and Griffin, 1976; 1977; Reese and Lin, 1989; 1991a-b; Reese et al., 1994; Reese and Mohamed, 1985; Reese et al., 1986a; Reese et al., 1986b; Reese and Orban, 1986; Reese et al. 1991; Reese and Stone, 1987, 1995; Reese and Tan, 1983; 1986a-b; Reese and Zander, 1987; 1988). Yet, it is clear that circumscription of the Calymperaceae remains problematic and inviting of further study.

Circumscription of genera within the family. Calymperes appears to be at least a phenetically natural group, and has distinctive characters such as its calyptra position, lack of a peristome, and spore dispersal mechanisms (Edwards, 1980b). Syrrhopodon also seems phenetically natural (Reese, 1993c), although as pointed out by Reese (in Allen, 1994) there is troublesome intergradation in many characters between Calymperes and Syrrhopodon. Thyridium (nom. illeg.), renamed Mitthyridum by Robinson (1975), appears to be a monophyletic clade derived from Syrrhopodon (Reese et al., 1986b). Mitthyridium is the only genus within this family that has a prostrate habit and orthotropic branches bearing teminal sporophytes. Another distinguishing feature of Mitthyridium, possibly apomorphic, is the presence of a strong border of hyaline cells which form a single layer.

The other genera once recognized in the family by Fleischer (1904, 1923) and by Brotherus (1924), Calymperopsis and Hypodontium, are of some debate. Although accepted by some authors (e.g., Fleischer 1904, 1923; Brotherus, 1924; Tixier, 1967; Edwards, 1980a), others (e.g., Florschutz, 1964; Reese, 1978; Crum and Anderson, 1981; Reese et al., 1986a) do not find the characters used for delineation of Calymperopsis to be of generic importance; and additionally, while morphologically distinct from Syrrhopodon, Hypodontium seems more correctly placed in the Pottiaceae (Reese et al., 1986a).

Specific consideration of Mittyhridium; taxonomy, history, and previous study.Mitthyridium is known exclusively from the paleotropics (Reese, 1993c), and was partially revised by Nowak (1980), who included keys, descriptions, illustrations, and distribution maps in her valuable treatment. More recently, Reese et al. (1986b) provided a thorough synopsis of the Mitthyridium as it occurs in Malaysia and adjacent islands. The genus appears to be monophyletic as a group, but it is taxonomically difficult within, since circumscriptions of species are weak, debated, and often changed (Reese et al., 1986a-b; Reese et al., 1994; Reese, 1994a). Still, relatively few species, within four subgenera (Reese, 1994a), have been described for this genus (Table 1), especially in relation to its huge sister genera, Calymperes and Syrrhopodon. This relative lack of species descriptions may be attributed to Mitthyridium's confinement to the paleotropics which relatively few studies have been targeted (e.g., Allen, 1987; Bartam, 1933a-b; 1936; 1939; 1940; 1945; 1950; 1951; 1956; 1957a-b; 1960a-c; 1961; Brotherus, 1924; Dixon, 1916; 1924; 1932; 1935; Dixon and Greenwood, 1930; Eddy, 1988; Menzel and Schultze-Motel, 1990; Nowak, 1980; Touw, 1971; 1978; 1974; 1992; Schultze-Motel, 1963; Tixier, 1966; Whittier, 1976; Whittier and Whittier, 1987).

Table 1: A taxonomic summary of Thyridium and Mitthyridium as treated in 1. Index Muscorum (1969), 2. Robinson (1975), 3. Nowak (1980), 4. Reese et al. (1986b), and 5. the Index of Mosses (1963-). Reference numbers for all 67 specific and infraspecific names published to date; asterisks (*) indicate synonyms according to that reference and the species taxon to which it was assigned; the geographical location abbreviations are according to Index Muscorum. N= considered in other genus besides Thyridium in Index Muscorum; - = not treated by that reference.

SpeciesAuthorityGeographical Location12345
1M. adpress um (Broth.) Robins.As 41164 *-1
2M. african umMitt.Afr 2N----
3M. adamenseBesch.As 3N----
4M. bescherelliiFleisch.As 4. OcN----
5M. binsteadii(Ther. et Dix) Robins.As 455--5
6M. borneense(Hamp. ) Kindb.As 3,4. OcN----
7M. cardotii(Fleisc h.) Robins.As 4777-7
8M. ceyloneseFleisch.As 3N----
9M. chenagonii (Ren. et Card.) Robins.Afr 399--9
1 0M. codono blepharum(C. Muell.) Kindb.As 4N--64 *-
1 1M. constrictum(Sull.) Robins.As 2-4. Oc1111111111
1 2var. neo-caledonicum(Ther.) Miller et al.As4. Oc---11 *-
1 3var. tahiticum(Besch.) Miller et al.As4. Oc---11 *-
1 4M. crassinerveMitt.OcN----
1 5M. crassum(Broth.) Robins.As 41515151615
1 6M. cuspidatum(Fleisch.) Robins.As 3,4161623 *-16
1 7M. cyrtophyllum(Besch.) Robins.Afr 31717--17
1 8M. fasciculautm (Hook. et Grev.) Robins.As 2-4. Afr 3. Am 6. Austr 1. Oc1818181818
1 9var. cardotii(Fleisch.) A. EddyAs 2-4----19
2 0subsp. obtusifolium(Lindb.) MenzelAs 4----20
2 1var. zollingeriFleisch.As 421--18 *-
2 2var. rhizophyllum(Broth. et Par.) NowakOc---2222
2 3M. flavum (C. Muell.) Robins.As 4232223-23
2 4var. ovatifoliumFleisch.As 424----
2 5M. fleischeri(Schu.-Mot.) Robins.As 4. Austr. 1. Oc.---47 *25
2 6var. ovatifoliumFleisch.As 4-----
2 7M. geheebii(Par.) Robins.As 4272764 *-27
2 8M. glaucinum(Besch.) Robins.Oc2828-47 *28
2 9M. gracileBroth.As 427 *----
3 0M. indicumMitt.As 3N----
3 1M. jungquilianum(Mitt.) Robins.As 4313131-31
3 2M. letestui(Ther. et P. Varde) Robins.Afr 23232--32
3 3var. scalariformeDemar. et LeroyAfr 233----
3 4M. leucoloma(C. Muell.) Robins.As 43434-3434
3 5M. louisiadum(Broth.) NowakAs 4--52 *3535
3 6M. luteum(Mitt.) Robins.Oc3636363636
3 7M. luzonense(Williams) Broth.As 423 *-23 *--
3 8M. manii(Fleisc h.) Robins.As 3,4. Oc3838-35 *38
3 9var. minusFleischAs 439--35 *-
4 0M. megamorphum(Fleisch.) Robins.As 44040--40
4 1M. micholitziiBroth. in C. Muell.As 441--34 *-
4 2M. micro-undulatum(Dix.) Robins.Afr 34242--42
4 3subsp. comoroenseReeseAfr 3----43
4 4M. nicobaricumBroth.As 3, 4. Austr 1--23 *--
4 5M. obtusifolium(Lindb.) Robins.Oc4545454545
4 6var. neocaledonicum(Ther.) Miller et al.Oc---57 *-
4 7M. papuanum(Broth.) Robins.As4. Oc474736 *4747
4 8M. parvifoliumBartr.Oc484852 *4848
4 9M. parvulum(Jaeg.) Robins.As 34949--49
5 0M. perundulatum(Broth.) Robins.As 4505031 *-50
5 1M. pungens(Dix.) Robins.As 45151--51
5 2M. repens(Harv.) Robins.As 3, 4. Austr 1525252-52
5 3var. minor(Fleisc h.) Tan et MohamedAs 3----53
5 4M. retusum(Besch.) ReeseAs 3----54
5 5M. revolutum(Doz. et Molk.) Kindb.As 3,4. Afr 2,3. Austr 1. OcN----
5 6M. rubiginosum(Mitt.) Jaeg.Am 4N----
5 7M. samoanum(Schu.-Mot.) Robins.As 4. Oc-5745 *5757
5 8M. subfasciculatum(Hampe) Robins.Austr. 15858-45 *58
5 9M. subflavum(Ren. et Card.) Robins.Afr 35959--59
6 0M. subluteum(C. Muell.) NowakOc60-606060
6 1M. subobtusifolium(Broth. et Par.) Robins.Oc6161-6161
6 2M. subrepensJaeg.As 452 *----
6 3M. undulatulum(Broth. et Geh.) Fleisch.As 4. Austr 1. Oc636352 *-63
6 4M. undulatum(Doz. et Molk.) Robins.As46464646464
6 5M. vriesei(Lac.) Robins.As 4656523 *6565
6 6M. wallasii(C. Muell.) Robins.As 4666666-66
6 7var. crassum(Broth.) MenzelAs 4----67

The remarkably local distribution of many Mitthyridium species, unusual for a moss group, may indicate a situation where a youthful clade is actively diversifying. Reese et al. (1986b) speculate (and probably correctly so) that Mitthyridium is a currently diversifying, recent derivative of the more pantropical, paraphyletic group Syrrhopodon (which may partially account for its blurred species distinctions and narrow distributions). We hope to be able to infer approximate time and place of origin for Mitthyridium and thus gain an opportunity to explore such macroevolutionary processes as diversification and clade formation, changes within lineages, and relative dispersability over time.

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